Deaerating system



1,669,673 J-. PRICE DEAERATING SYSTEM Filed April 4, 1925 3 I INVENTOR ORNEY Patented May 15, 1928.

UNITED STATES 1,666, 73 PATENT OFFICE. j

JOSEPH PRICE, OF STAPLETON, NEW YQBK, ASSIGNOB TO THE GRISCOH-BUSSELL COMPANY, 01' NEW YORK, 11'. Y., A CORPORATION 01 DELAWARE.

DEAEBATING SYSTEM.

Application filed April 4, 1925. Serial No. 20,859.

This invention relates to the deaeration or degassing of boiler feed water and has to do particularly with the storage of the deaerated water in such fashion as to satisfactorily maintain it in its deaerated condition until such time as it may be drawn into the boiler feed line for use as makle-up water in the system.

Considerable difiiculty has been expe rienced in steam generating systems from deterioration of boilers, piping and other apparatus due to the presence of various gases, notably oxygen, dissolved in the feed water as it is supplied to the system. These gases are liberated from the water at the high temperatures attained during the steam generating process and combine with the metal of the containing pipe lines and apparatus. Raw water of the sort ordinar1ly available as ,boiler feed make-up in a steam generating plant contains large quantities of air in solution so that the amount of oxygen and other gases which are liberated as the temperature of the water rises is suflicient to exert a very considerable deteriorating action on the metal parts of the system.

For successful operation it is therefore necessary that the raw water" su plied .to the boiler feed system be freed rom substantially all of its contained gases before it is admitted to the system. Deaeration of this water is accomplished by heating the water. or otherwise controllin the pressure and temperature relations a ectin'g the water in such fashion that the dissolved gases are permitted to escape from the liqby permitting the water to remain subected length to these'conditions for a sufiicient of time, substantially complete deaeration ma be accomplished.

The puri ed water from the deaeratingapparatus is passed into the system to be sent to the boiler as feed water. Since the demands of the boilerfeed system for depractice to efiectthe removal of presure reducing valve, the resultin feed system. The tank is constantly being supplied with purified water from the deaerator. It is a means of rendering the system flexible so that'although the purified water from the deaerator may be supplied at a substantially constant rate, the oiler feed pumps may draw upon the water supply in the feed tank and satisfy the boiler requirements independently of the rate V at wh ch the deaerator can furnishair-free make-up water..

In order to prevent the deaerated water again becoming contaminated with injurious gases, precautions must be taken to avoid the access of such gases to the water stored in the feed tank. This may be, done by filling the space in the tank above the liquid with steam to thus exclude the air from the liquid and in this fashion prevent contamination. According to the usual practice, this steam blanketm of the water in the feed tank is accompfished by withdrawing steam from the auxiliary exhaust line or other source of steam supply and passing a proper amount of it into the feed tank through the medium of a pressure reducing valve. This system is open to a number 0 objections from the standpoint of practical operation of the system among which may be mentioned the fact that pressure reducmg valves of the type now available are not re iable when the pressure at the low pres sure side of the valve is'at or near atmospheric. should, of course, be at or near atmospheric for the reason that in case of failure of the mcreased ressure in the feed tank wi danger t e tank, which apparatus is common y built to withstand only light pressure.

In the system of the present invention, the steam for blanketing the feed tank is obtained from the auxiliary .steam main or other source of supgly and the pressure of the steam as it is a itted to the feed tank The pressure in the feed tank aerated water do not strictly correspond to, is reduced to the proper yalue without necesno ltI ' sity of employing a pressure reducing valve.

present continually enters this condensing.

passage and thereby .prevents undesirable pressure rise in the apparatus. The condensate forming in the condenser unit-is conducted out of the apparatus and may be returned to the deaerator or otherwise disposed of as desired, while the n0n-condensable gases escape through a vent. In this fashion the purified water in the feed tank is at all times excluded from the action of gases which might become redissolved in the liquid and render'it unfit for boiler feed purposes. The system permits the feed tank to be maintained at substantially atmospheric pressure and for this reason, as well as for its extreme simplicity the system is particularly well adapted to installation in existing power plantsin such fashion that the existing head of water across the boiler feed pump will not be affected.

A preferred embodiment of the invention is illustrated in the accompanying drawingsin which Figure 1 is a somewhat diagrammatic view illustrating a deaerating system embodying the present invention, and Figure 2 is a view showing a structural detail of the apparatus.

Referring to the drawings, 1 indicates the deaerating apparatus in which the expulsion of the contained gases is accomplished. This apparatus is of the type wherein the heat for bringing the temperature of the water under treatment to the boiling point is derived from the auxiliary exhaust steam which is supplied through the line 2 to the tube bundle 3 constituting the heat transferring element of the apparatus. The incoming water, which consists chiefly of the turbine condensate supplied to the deaerator through the line 4 and the miscellaneous hot water returns furnished through the line 5, enter at the top of the apparatus and through the medium of distributing tray 6 and also the top tray 32 is passed down upon the heating element 3 in the form of a rain or spray which serves to thoroughly distributethe main portion of the liquid over the tube surfaces of the heating element. The liquid which is thus distributed as a film over the heating surfaces of the tubes 3 is effectually deaerated and drips down into the bottom part of the deaerator from whence it is withdrawn by the extraction pump 7. The vapors and uncondensable gases evolved in the deaerating chamber are drawn out at the top of the chamber through the medium of the air ejector 8 which is preferably operated by a source of live steam supplied through the line9. The steam used to operate the ejector as well as the vapors withdrawn from the deaerating chamber are condensed in the coil 10 placed in the turbine condensate line so that the condensingof these Japors serves to preheat the turbine condensate on its way to the deaerator and thus effect a corresponding economy in operation. A vent 11 is provided at the outlet end of the coil 10. for the purpose of discharging the air withdrawn from the dederator by the ejector 8 while the condensate is passed back into the deaerating chamber through the medium of a trap 12 and line 13.

Condensate from the main heating element 3' is discharged through the trap 14 and is passed into the deaerator through the line 15.

The feed or surge tank for storing the deaerated water is indicated at 16. This tank 16 is supplied with purified water directly from the deaerator through the medium of the pump 7 and the connecting line 17. An overflow pipe 18 is provided on the feed tank 16 so that it at any time an excess amount of water is furnished to the tank such excess may escape without injury to the tank. Water is withdrawn from the feed tank 16 by means of the boiler feed pump 19 and is passed through the line 20 to the boiler feed open heater or other convenient part of the boiler feed system.

In order to prevent the contamination of the liquid stored in the tank 16 with injurious gases, the space 21 above the liquid level is kept full of steam. Steam for this purpose is derived from the auxiliary exhaust line or other source of supply and is suthciently free from'air to be satisfactory for the purpose. Steam from the auxiliary exhaust line is conveyed to the feed tank 16 through the line 22 entering at the top of the feed tank as indicated at' 23. The flow of steam into the feed tank is restricted by an orifice 24.- provided in the line preferably at a point adjacent the feed tank. This orifice may be constituted as shown in Figure 2 wherein an orifice plate 25 containing a small centrally disposed circular orifice is inserted between-the flanged ends 26 of the members constituting the pipe line 22. As is well known, the provision of such an orifice results in a predetermined fiow of steam into the feed tank for. a given pressure difierential between the source of steam supply and the tank.

The blanketing steam accumulating in the space 21 above the water in the feed tank upper end as indicated at 28. The steam neeaeva entering the coil through the opening 28 is condensed during its passage throu h the coil and the condensate is; disc arg through the trap29 and sent back .to the deaerator 1 through the line '30. Any air which may pass the coil 27 with the condensate is vented toatmosphere through a pipe 31.

The coil 27 furnishes a path of egress for the blanketing steam from the feed tank 16. Inasmuch as the condensate passing the coil 27 is'vented to atmosphere the pressure in the feed tank will be substantially atmos- Eheric. It the pressure tends to build up a ow of the blanketing steam through the condenser coil 27 will occur with theresult that an equilibrium pressure at or slightly above atmospheric is automatically maintained. The orifice structure 24 will be of such capacity as to permit steam to flow into the feed tank 16 at a rate corresponding to the maximum rate atwhich the boiler feed pump 19 can empty the tank. By this means, a complete blanket of steam is maintainedj above the waterstored in the tank 16 under all conditions of operation and is so' maintained without any attention whatever on the part of the operator.

The parts of the system are of the utmost simplicity. with the result thati'the cost of installation is correspondingly low. The feed tank is at all times efiectually protected .from dangerous pressures. The s stem provides a means for deaerating 'theiler feed supply and for storing the deaerated water without trouble of contamination until such time as it shall be required for use in the system; The quantity of steam required to accomplish the blanketing of the tank is practically negligible. A further advantage is that the system automatically regulates for substantiallyatmospheric pressure in the tank so that the system is particularly a applicable to existing installations where it ed undisturbed.

- means for returning; r

'uncondensable gases w1 deaerator being e hire.

is desired to leave the pressure relations between the various parts of the apparatus I claim:

1. In a boiler feed system, a deaerator, a feed tank forstoring the deaerated water, a line for introducing steam to the spacev above the stored water in said feed tank means for permitting escape of a portion 0 said steam to avoid excessive ressures in said feed tank, means for con ensing said '65 steam by passing-1t into heat exchanglng relation with the liquid in said tank and an overflow connection provided on said tankto discharge excess water supplied to the tank.- '00 2. In a boiler feed system, deaerating ap- Y paratus comprising a shell for containing 7 the water to be treated, means for bringing auxiliary exhaust steam into heat exchanging' relation with the water under treatment to effect deaeration thereof, a steam ejector for withdrawingevolved vapors and gases from said deaerator, means ior preheating the incoming water by passing said withdrawn vapors 'and'gases into heat exchang-v 7o. ing relation therewith, a ing the deaerated'water, a line; for'introducing steam to the space above thestored water n said feed tank, means for permittin escape of a portion of said steam to avoid excessive pressures in said feed tank including a condensing element in said tank,'and

to said deaerator the condensate imuing om'the heating element of said deaerator, the condensate resulting fromthe vapors withdrawn from the deaerator and the condensate issuing from the condensing element of said f 4 tank, the

'thdrawn from, lled from the system. ereof I. afiix'my signe V Josnrnrnlcn.

In testimony w feed tank for stor- I 

